Exhaust gas purification method and system

ABSTRACT

A method and system for reduction of particulate and gaseous contaminants from exhaust gas including multiple gas handling systems, a mixing tank, and a mixing system that mixes unprocessed exhaust gas and system fluid, while agitating the system fluid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. nonprovisional applicationSer. No. 16/109,604, filed on Aug. 22, 2018, all of which isincorporated by reference as if completely written herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

TECHNICAL FIELD

The present disclosure relates generally to a system and method forreducing contaminants from exhaust gas.

BACKGROUND OF THE INVENTION

The present invention relates to a method for reduction of particulateand gaseous contaminants from exhaust gas. While much of this disclosurewill refer to coal fired power plants, the present system and method isnot limited to exhaust gas that is the result of the combustion of coal,and further is not limited to flue gas associated with the combustion ofother fuels such as natural gas, diesel, waste oil, garbage, and thelike, rather the present system and method is applicable to any exhaustgas stream from which it is desirable to remove contaminants,particularly any gas stream application that may currently utilizeprecipitator, scrubber, and any other, technologies to removecontaminants.

With that out of the way and now referring back to combustion exhaustgas, particulate matter carried in suspension by the effluent or wastegases from furnaces burning fossil fuels is commonly referred to as flyash. Fly ash is an undesired by-product of coal fired power plants. Thefly ash created by power plants can greatly vary depending on the typeof coal used as fuel. For instance lignite coal produces Class C fly ashthat is high in lime (CaO), which is commonly formed into blocks. Inanother example, anthracite and bituminous coals produce Class F fly ashwhich is naturally low in lime (CaO). As a result, power plants, andtheir pollution control systems, are generally designed specifically forthe type of fuel used in order to adequately to reduce particulate andgaseous contaminants from the exhaust gas. In the past, the dumping ofuntreated power plant exhaust gas resulted in acid rain that damagedbuildings and plants, introduced high concentrations of heavy metalssuch as mercury (Hg) and cadmium (Cd) in the environment, as well asparticulate dust that covered buildings and proved hazardous to personswith respiratory problems. Due to the serious damage untreated exhaustgases have on the environment, EPA regulations have been implemented toprevent the dumping of untreated power plant exhaust gases directly intothe environment. Unfortunately, power plants create large amounts of flyash each day that must be properly disposed of. For example, a powerplant with large boiler rated at 1,400,000 lb./steam/hr. typically willemit 700,000 cfm of waste gas and 140 tons of ash/day. Some plants thatproduce Class C fly ash turn a portion of the fly ash into cinder blockswhich helps to recoup a portion of the added expense of fly ashdisposal. Power plants that produce Class F fly ash, due to low limecontent of the ash, a binder such as Portland cement must be added tothe fly ash in order to create cinder blocks, as a consequence costingthe power plant more money to dispose of the fly ash. Currently, 3 to 4%of the total capital investment goes to high-efficiency ash-collectingand handling equipment.

Due to the need to prevent damage to the environment from pollutants andfly ash emitted from power plants, almost all pulverized coal powerplant boilers incorporate high efficiency exhaust gas cleaningequipment. Many factors determine collection efficiency of a powerplants fly ash and other pollutants. For instance, mechanicalfeasibility, the footprint of the allocated land, and profitability allplay a role in determining what equipment a power plant can use and thepollutant collection efficiency.

Fly ash collection equipment usage has increased as boilers are designedto use coal with higher ash content and increased output. For example,earlier power plant installations had a 90% collection efficiencyrequirement, whereas modern power plants have 95 to 98% fly ash andpollutant collection efficiency. Variability in fly ash characteristicscomplicates fly ash and pollutant collection even with the advancementof power plant furnace design and pollution collection methods.

Coal fired power plants use a plurality of methods and equipment toreduce fly ash and other pollutants from being emitted into theenvironment. For instance, electrostatic precipitators are commonly usedto separate particulate matter from the exhaust gas. Electrostaticprecipitators use a direct current high voltage to induce a charge onparticles in the exhaust gas. The charge causes the particles to movetowards and stick to grounded plates in the electrostatic precipitators.Unfortunately, electrostatic precipitators are only effective inremoving particulate matter, such as fly ash, from the exhaust gasstream. Vertical wet scrubbers are also used to clean the exhaust gasstream of particulate matter and other pollutants. In a vertical wetscrubber, exhaust gases flow in an upwards fashion while a mist insprayed into the exhaust gas stream. As the mist travels down thevertical wet scrubber tower, the mist collects particulate matter in theexhaust gas stream and deposits them in the bottom of the tower.Additionally, various chemical agents may be included in the mist toreact with pollutants in the exhaust gas. Some of these pollutantsinclude sulfur dioxide (SO₂), mercury (Hg), and other heavy metals. Suchsystems are illustrated in FIG. 1.

SUMMARY OF THE INVENTION

A method and system for reduction of particulate and gaseouscontaminants from exhaust gas including multiple gas handling systems, amixing tank, and a mixing system that mixes unprocessed exhaust gas andsystem fluid, while agitating the system fluid.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

Without limiting the scope of the as disclosed herein and referring nowto the drawings and figures:

FIG. 1 is a schematic of a typical coal fired power plant;

FIG. 2 is a schematic of an embodiment of a coal fired power plantincorporating aspects of the present invention;

FIG. 3 is a schematic of an embodiment of a coal fired power plantincorporating aspects of the present invention;

FIG. 4 is a schematic, in side elevation view, of an embodiment of thepresent invention;

FIG. 5 is a schematic, in top plan view, of an embodiment of the presentinvention;

FIG. 6 is a side elevation view of an embodiment of the mixing tank andmixing system of the present invention;

FIG. 7 is a side elevation view of an embodiment of the mixing tank andmixing system of the present invention;

FIG. 8 is a side elevation view of an embodiment of the mixing tank andmixing system of the present invention;

FIG. 9 is a side elevation view of an embodiment of the mixing tank andmixing system of the present invention;

FIG. 10 is a schematic, in top plan view of a section, of an embodimentof a diffusion chamber of the present invention;

FIG. 11 is a schematic, in top plan view of a section, of an embodimentof a diffusion chamber of the present invention;

FIG. 12 is a schematic, in top plan view of a section, of an embodimentof a diffusion chamber of the present invention;

FIG. 13 is an isometric view of an embodiment of a diffusion chamber ofthe present invention;

FIG. 14 is a schematic, in side elevation view, of an embodiment of thepresent invention;

FIG. 15 is a schematic, in side elevation view, of an embodiment of thepresent invention;

FIG. 16 is a side elevation view of an embodiment of the mixing tank andmixing system of the present invention; and

FIG. 17 is a side elevation view of an embodiment of the mixing tank andmixing system of the present invention.

These illustrations are provided to assist in the understanding of theexemplary embodiments of the method and system of reducing exhaust gascontaminants described in more detail below and should not be construedas unduly limiting the specification. In particular, the relativespacing, positioning, sizing and dimensions of the various elements andcomponents illustrated in the drawings may not be drawn to scale and mayhave been exaggerated, reduced or otherwise modified for the purpose ofimproved clarity. Those of ordinary skill in the art will alsoappreciate that a range of alternative configurations have been omittedsimply to improve the clarity and reduce the number of drawings.

DETAILED DESCRIPTION OF THE INVENTION

As seen in FIGS. 1-15, the presently disclosed method and system forreduction of particulate and gaseous contaminants from exhaust gasenables a significant advance in the state of the art. It is a new andnovel method for reduction of particulate and gaseous contaminants fromexhaust gas comprising conveying exhaust gas from a source (100) to amixing tank (300). The unprocessed exhaust gas composition depends uponthe fuel being burned. For instance, pulverized coal combustion flue gaswill have an average constitution of: 76% N₂; 6% O₂; 11% CO₂; 6% H₂O; 1%Ar; 500-800 ppmw NOx; <1% dioxane; 0.1-1 Hg ppmw; 0.1-1 Cd ppmw; 0.5-2other heavy metals ppmw; 5-20 g/m³ of dust; and those skilled in the artlikewise know the constituents of flue gases associated with other fuelssuch as natural gas, diesel, waste oil, garbage, and the like. Theunprocessed exhaust gas composition is conveyed from the source (100) tothe mixing tank (300) through a first gas handling system (200), asillustrated in FIG. 4, having a first gas handling system flowrate. Thefirst gas handling system (200) includes a first gas handling systeminlet (202) that is in communication with the source (100), and a firstgas handling outlet (204) that is in communication with a mixing system(400), which is in fluid communication with the mixing tank (300).Furthermore, the first gas handling system (200) may include a first gashandling system fan (210) that insures a positive pressure of theunprocessed exhaust gases entering the mixing system (400).

The mixing tank (300) may include a mixing tank drain (310), a mixingtank drain valve (320), which may be manual or automatically controlled,and a mixing tank system fluid (330). Additionally, in one embodimentthe system fluid (330) is primarily water, but may include system fluidadditives containing various compounds to neutralize various chemicalscommonly found in flue exhaust gases. For instance, the system fluid(330) may contain, but not limited to, hydrated lime (Ca(OH)₂) toneutralize sulfuric acid (H₂SO₄) that is formed when burning coal thathas sulfur in it. Burning coal releases sulfur dioxide (SO₂) whichreacts with water (H₂O) which forms sulfurous acid (H₂SO₃). Thesulfurous acid (H₂SO₃) reacts further with water (H₂O) to form sulfuricacid (H₂SO₄). Lime (Ca(OH)₂) may be incorporated to react with thesulfur dioxide(SO₂) to form calcium sulfite(CaSO_(3(s))) and water, asseen in the equation below.

Ca(OH)₂+SO₂→CaSO₃+H₂O

In this embodiment, the calcium sulfite precipitates out of the systemfluid (330) and settles in the bottom of the tank (300). Furthermore,the mixing tank drain (310) allows for the removal of precipitates andparticulate from the tank (300) by opening the mixing tank drain valve(320). Again, the system fluid additive is not limited to hydrated lime(Ca(OH)₂), but may be one or more other chemical compounds. Forinstance, in further embodiments, limestone CaCO₃, magnesium hydroxide(Mg(OH)₂), and lye (NaOH) may be used to remove sulfur dioxide (SO₂)from the unprocessed exhaust gas. The system fluid additive(s) may beintroduced into the system fluid (330) within the mixing tank (300) viaan additive system (500), seen in FIG. 4, which may be as simple as acompartment within the mixing tank (300) to receive and house additives,however in another embodiment it may be an additive injection systemthat monitors the system fluid (330) and injects at least one additivewhen the additive system (500) determines that the system fluid (330)requires more additive to carry out the objectives set forth herein.

The mixing tank (300) may have mixing tank monitoring system having aliquid sensor system that monitors the amount of precipitant and othercontaminants in the mixing tank (300). The sensor system may include amixing tank fluid sensor (350) seen in FIG. 4. The sensor system is setwith at least one threshold mixing tank contaminant levels, and upon atleast one threshold mixing tank contaminant level being exceeded, aportion of the system fluid (330) is drained from the tank. In oneembodiment the system fluid (330) is refreshed with new unreacted systemfluid (330). The mixing tank fluid sensor (350) may monitor one, ormore, of the following: physical precipitant levels, total dissolvedsolids, conductivity, specific gravity, pH level, mercury (Hg), Lead(Pb), and other heavy metal levels, as well as the temperature of thesystem fluid (330). In one particular embodiment the at least onethreshold mixing tank contaminant level is the total dissolved solids inthe system fluid (330) and is set to not exceed 15,000 mg/1, or 22,500mmhos of conductivity.

Similarly, mixing tank monitoring system may have a gas sensor systemthat monitors the gas in the mixing tank (300), which may include amixing tank gas sensor (340). The mixing tank gas sensor (340) maymonitor one, or more, of the following: physical particulate levels,carbon monoxide, carbon dioxide, sulfur dioxide, and various oxides ofnitrogen (NOx), as well as the temperature of the gas within the mixingtank (300). As discussed in more detail later, a mixing tank controlsystem may be in communication with the mixing tank monitoring systemand control aspects of the mixing system (400), the first GHS fan (210),the second GHS fan (610), the mixing tank drain valve (320), and/or anyof the dampers or valves disclosed, or shown in the figures.

The mixing tank (300) has a total mixing tank volume, a mixing tankliquid volume, which is the volume of the system fluid (330) containedin the mixing tank (300), and a mixing tank gas volume, which is thedifference between the total mixing tank volume and the mixing tankliquid volume. Throughout the specification numerous unique relationshipare disclosed, each such relationship being critical to the performanceof embodiments of the system and method. In one embodiment, one suchrelationship is that of the first gas handling system flowrate to themixing tank liquid volume, the mixing tank gas volume, and/or the totalmixing tank volume. As will be explained in more detail later, whileFIG. 4 schematically illustrates a system and method utilizing a singlemixing tank (300), multiple mixing tanks (300, 300 a, 300 b, 300 c) maybe utilized in parallel, as seen in FIG. 5, or in series, as seen inFIG. 15. In the case of parallel mixing tanks (300), the first gashandling system (200) may direct the unprocessed exhaust gas to a singlemixing tank (300) at a time, or alternatively multiple mixing tanks(300) simultaneously. Thus, these first series of unique relationshipsrelate to the mixing tank liquid volume, the mixing tank gas volume,and/or the total mixing tank volume of one mixing tank (300), ormultiple mixing tanks (300) if used simultaneously, used in the initialtreatment of the unprocessed exhaust gas. For example with reference toFIG. 2, if only a single mixing tank (300) is used in the initialtreatment of the unprocessed exhaust gas at any one time, and the othersare standby mixing tanks (300) for use during the service of anothermixing tank, then these disclosed relationships are only related to thevolumes of a single mixing tank (300); whereas if two or three of themixing tanks (300) are simultaneously used in the initial treatment ofthe unprocessed exhaust gas, then these disclosed relationships arerelated to the combined volumes of the simultaneously used mixing tanks(300).

Now returning to the previously mentioned relationships, in oneembodiment one such relationship is that of the first gas handlingsystem flowrate to the mixing tank liquid volume, the mixing tank gasvolume, and/or the total mixing tank volume. In one embodiment themixing tank liquid volume is at least 0.1 gallons per CFM (cubic feetper minute) of the first gas handling system flowrate; thus, a systemhaving a first gas handling system flowrate of 10,000 CFM would have amixing tank liquid volume of at least 1,000 gallons. In a furtherembodiment the mixing tank liquid volume is 0.1-5.0 gallons per CFM(cubic feet per minute) of the first gas handling system flowrate; thus,a system having a first gas handling system flowrate of 10,000 CFM wouldhave a mixing tank liquid volume of 1,000-50,000 gallons; while in yetanother embodiment the mixing tank liquid volume is 0.2-3.5 gallons perCFM (cubic feet per minute) of the first gas handling system flowrate;and in an even further embodiment the mixing tank liquid volume is0.2-1.5 gallons per CFM (cubic feet per minute) of the first gashandling system flowrate.

In another embodiment the mixing tank gas volume is at least 0.013 cubicfeet per CFM (cubic feet per minute) of the first gas handling systemflowrate; thus, a system having a first gas handling system flowrate of10,000 CFM would have a mixing tank gas volume of at least 130 cubicfeet; while in another embodiment the mixing tank gas volume is at least0.020 cubic feet per CFM (cubic feet per minute) of the first gashandling system flowrate; while in still a further embodiment the mixingtank gas volume is 0.013-0.667 cubic feet per CFM (cubic feet perminute) of the first gas handling system flowrate; and in yet anotherembodiment the mixing tank gas volume is 0.013-0.334 cubic feet per CFM(cubic feet per minute) of the first gas handling system flowrate. Evenfurther, another embodiment has identified a unique relationship betweenthe mixing tank gas volume and the mixing tank liquid volume to furtherimprove the performance and reliability of the system and method, whilealso reducing the likelihood of damage to the mixing tank (300) shouldany of the associated systems fail. For example, in one particularembodiment the mixing tank gas volume is at least 50% of the mixing tankliquid volume, while in another embodiment the mixing tank gas volume isat least 75% of the mixing tank liquid volume, in still anotherembodiment the mixing tank gas volume is greater than the mixing tankliquid volume, while in yet another embodiment the mixing tank gasvolume is no more than twice the mixing tank liquid volume, including nomore than 150% of the mixing tank liquid volume in still a furtherembodiment. Such relationships are essential to allowing the mixingsystem (400) to safely operate for extended periods of time, at highflowrates containing high particulate loads, while achieving theeffectiveness and goals described herein. In an embodiment the first gashandling system flowrate is at least 5000 cfm, while it is at least10000 cfm in another embodiment, at least 50000 cfm in still a furtherembodiment, and is at least 100000 cfm in an even further embodiment. Infact, a large scale industrial embodiment of the system and method mayhave a first gas handling system flowrate in excess of 250000 cfm, andin a particularly large-scale embodiment it is in excess of 500000 cfm,thus one skilled in the art will appreciate that the gas handlingsystems described herein may incorporate multiple ducting systems andfans routing exhaust gas to large mixing tanks and mixing systemsincorporated numerous pumps.

Now referring to FIG. 5, the method and system for reduction ofparticulate and gaseous contaminants from exhaust gas may comprise ofmultiple parallel mixing tanks (300). One benefit of using multiplemixing tanks (300) is that multiple mixing tanks (300) allow forcontinuous exhaust gas processing by redirecting the exhaust gases to afresh mixing tank (300) when a previously used tank needs servicing, orduring the system fluid (330) refreshing process. As illustrated, themethod and system may utilize a first GHS fan (210) that feeds any, orall, of the parallel mixing tanks (300) with the flow controlled bymotor actuated dampers, or each of the parallel mixing tanks (300) mayhave their own dedicated first GHS fan (210), not illustrated but easilyunderstood by one skilled in the art. Another benefit of using multiplemixing tanks (300) is that the system has additional exhaust gashandling capacity. During times of lower electrical power consumption,the plant may not be burning as much fuel and therefor generating lessexhaust gas. As such, one or more of the mixing tanks (300) can be idledto save energy. In times of high electrical consumption, all the mixingtanks (300) can be used.

In another embodiment, the method for reduction of particulate andgaseous contaminants from exhaust gas may comprise of multiple seriesmixing tanks (300 a, 300 b, 300 c), as seen in FIG. 15. In thisembodiment, in order to progressively scrub the exhaust gas, the exhaustgas passes through multiple mixing tanks (300 a, 300 b, 300 c). In onevariation, each mixing tank (300 a, 300 b, 300 c) contains a systemfluid additive, or chemical reagent, to target specific pollutants foundin the exhaust gas. For instance, one mixing tank (300 a, 300 b, or 300c) may contain hydrated lime (Ca(OH)₂) to react with the sulfur dioxide(SO₂) in the exhaust gas. In the next tank the system fluid additive, orchemical reagent, it may include an oxidant like sodium chlorite(NaClO₂) and/or nitrogen oxide (NO_(x)) which reacts with elementalmercury (Hg) to form mercury oxide (HgO) and mercury (II) chloride(HgCl₂) which are captured by the system fluid (330) and precipitatewithin the mixing tank (300 a, 300 b, or 300 c). The mixing tank controlsystem may control the activation and deactivation of parallel or seriesmixing tanks (300 a, 300 b, 300 c) to achieve the objectives discussedherein. For example, in an embodiment of FIG. 15, the first mixing tank(300 a) may be the primary tank and the mixing tank control system mayonly activate subsequent mixing tanks (300 b, 300 c), associated mixingsystems (400 b, 400 c), and/or associated gas handling systems anddampers, when the mixing tank fluid sensor (350) and/or mixing tank gassensor (340) measure a value outside of a predetermined acceptable rangestored in the mixing tank control system.

Now referring to the mixing system (400) seen in FIGS. 4 and 6, themixing system (400) selectively mixes the unprocessed exhaust gas andthe system fluid (330), while agitating the system fluid (330), toremove particulate and contaminants from the unprocessed exhaust gas.The mixing system (400) may include a mixing pump (410), as seen in FIG.7.

Others have written about the application of a turbulent contactabsorber for the absorption of SO₂ and the simultaneous removal of flyash in a coal-fired power plant, as well as recognizing that particlesaround 1 μm and below 1 (submicrometer) are present in small amounts inthe total particulate mixture yet have serious impacts on human healthand the environment, none have disclosed the presently disclosed uniqueembodiments and relationships as claimed herein, particularly the use ofa mixing pump (410) to mix unprocessed exhaust gas and system fluid(330), to increase the quantity of unprocessed exhaust gas entrained inthe system fluid (330), reduce the size of the entrained gas bubbles,agitate the gas entrained system fluid (330), and in some embodimentsselectively spray the gas entrained system fluid (330) within the mixingtank (300). Thus, the particles that are difficult to remove using anyconventional scrubbers, namely those in the 0.1 μm to 0.5 μm range, areparticularly susceptible to capture using the present systems andmethods having a targeted removal efficiency of 95% to 100% forparticulate matter of sizes ranging from 0.1 μm to 100 μm.

A number of types of pumps are suitable for use as the mixing pump (410)provided it has the requisite capacity and can withstand the entrainedgas, particulate, and temperature to which it is exposed in the presentsystem and method. Such pumps include, but are not limited to,rotodynamic pumps, such as radial-flow pumps including centrifugalpumps, end suction pumps, horizontal split-case pumps, multi-stagepumps, multi-phase pumps, dissolved air flotation pumps, multi-volutepumps, submersible pumps, vertical turbine pumps, and axial-flow pumps;positive displacement pumps, such as rotary-type positive displacementpumps including internal gear, screw, shuttle block, flexible vane orsliding vane, circumferential piston, flexible impeller, helical twistedroots (e.g. the Wendelkolben pump), liquid-ring, lobe, and peristaticpumps; reciprocating-type positive displacement pumps including pistonpumps, plunger pumps, and diaphragm pumps; and linear-type positivedisplacement pumps; impulse pumps; and jet pumps; just to name a few.

In some embodiments, unprocessed exhaust gas is combined with the systemfluid (330) within 50 feet of the inlet to the mixing pump (410)resulting in the mixing pump (410) shearing the unprocessed exhaust gasinto small bubbles, which in one embodiment results in the mixeddischarge from the mixing pump (410) containing an average bubble sizeof less than 100 μm, while in another embodiment the average bubble sizeis less than 75 μm, and in still a further embodiment the average bubblesize is less than 50 μm. Small bubble sizes increases the surface areaof the bubbles in contact with the system fluid (300) and promotesimproved particulate and contaminant capture. In yet another embodimentthe unprocessed exhaust gas is combined with the system fluid (330)within 25 feet of the inlet to the mixing pump (410), and within 15 feetof the inlet to the mixing pump (410) in still a further embodiment, andwithin 5 feet of the inlet to the mixing pump (410) in yet anotherembodiment, as seen in FIGS. 6-9.

While proximity of combination and bubble size are important, so too isthe percentage of exhaust gas entrained within the mixed discharge fromthe mixing pump (410), as low percentages of gas entrainment result inthe consumption of a tremendous amount of energy to circulate enoughsystem fluid (330) to process the exhaust gas, and lower quantities ofentrained gas bubbles reduce the efficiency of removing particulate andcontaminants from the exhaust gas. In one embodiment the mixed dischargeexiting the mixing pump (410) contains at least 6% exhaust gas entrainedin the system fluid (330), while a further embodiment has at least 8%exhaust gas entrained in the system fluid (330), and even furtherembodiments have at least 10%, at least 12%, at least 14%, at least 16%,and at least 18% gas entrainment. In another embodiment the mixeddischarge exiting the mixing pump (410) contains 6-40% exhaust gasentrained in the system fluid (330), while a further embodiment has8-35% exhaust gas entrained in the system fluid (330), yet anotherembodiment has 10-30% exhaust gas entrained in the system fluid (330),and still another embodiment has 12-25% exhaust gas entrained in thesystem fluid (330).

One skilled in the art will appreciate that many off the shelf entrainedgas tester, or EGT, devices are commercially available to measure thepercentage of entrained gas, and may do so in real-time, and may be incommunication with the mixing tank control system. The control systemmay automatically adjust the amount of unprocessed exhaust gas drawnthrough at least the auxiliary flow channel (240) to achieve a targetpercentage of entrained gas within the mixed system fluid, and/orautomatically adjust the amount of system fluid drawn through the atleast one orifice (480) to achieve a target percentage of entrained gaswithin the mixed system fluid. Further, not all types of pumps canhandle high levels of entrained gas. One particular embodimentincorporates a dissolved air flotation pump specifically designed forhigh levels of entrained gas, such as the HellBender DAF pumpdistributed by Environmental Treatment Systems, Inc. of Acworth, Ga., orthe multiphase DAF pumps of Shanley Pump and Equipment, Inc. ofArlington Heights, Ill. Another embodiment incorporates a multi-volutecentrifugal pump specifically designed for high levels of entrained gas,such as the LaBour TFA triple-volute centrifugal pump by Sterling FluidSystems, Inc. of Indianapolis, Ind. All details of these referencedpumps are incorporated by reference. In one embodiment the flowrate ofthe mixing pump (410) is at least 0.5 gallons per minute (GPM) per CFMof the first gas handling system flowrate, while in another embodimentthe flowrate of the mixing pump (410) is at least 1.0 gallons per minute(GPM) per CFM of the first gas handling system flowrate, and in yet aneven further embodiment the flowrate of the mixing pump (410) is atleast 2.5 gallons per minute (GPM) per CFM of the first gas handlingsystem flowrate. In still further embodiments, the high gas entrainmentand small bubble size achieves the desired effectiveness even withmixing pump (410) having a capacity of no more than 50 gallons perminute (GPM) per CFM of the first gas handling system flowrate, and nomore than 25 gallons per minute (GPM) per CFM of the first gas handlingsystem flowrate in a further embodiment, and no more than 10 gallons perminute (GPM) per CFM of the first gas handling system flowrate in stillanother embodiment. Thus, in light of the disclosed embodimentsregarding the first gas handling system flowrate, one skilled in the artwill appreciate that in some embodiments the mixing system (400) willinclude multiple mixing pumps (410). In a particularly effectiveembodiment the total capacity of the mixing pump (410), or pumps, isenough to circulate the total mixing tank liquid volume at least oneevery hour; while in another embodiment it circulates the total mixingtank liquid volume at least one every 45 minutes; and in still anotherembodiment it circulates the total mixing tank liquid volume at leastone every 30 minutes. However, in another series of embodiments whichfurther balance the need to circulate enough system fluid (330) to mixthe exhaust gas, while still ensuring the settlement of capturedparticulate and contaminants, the total capacity of the mixing pump(410), or pumps, does not circulate the total mixing tank liquid volumemore than once every minute; while in a further embodiment it does notcirculate the total mixing tank liquid volume more than once every 2minutes; while in a further embodiment it does not circulate the totalmixing tank liquid volume more than once every 5 minutes.

Often general purpose centrifugal pumps can only deal with airentrainment levels of 5 to 8 percent. One skilled in the art willappreciate that cavitation and entrained gas are related but distinctissues; with entrained gas, the liquid entering the pump already hasliquid and gas; in the pump it's liquid and gas; and the dischargecontains liquid and gas. Conversely, with most traditional cavitation,the liquid coming into the pump is fully liquid; as soon as it hits theinlet of the pump, it starts to vaporize and comes out as liquid. In oneembodiment the mixing pump (410) is a horizontal end suction pump with aFrances-vane impeller to handle the gas rich mixture and reduce thelikelihood of cavitation, while another embodiment incorporates astar-shaped impeller, with extended inlet vanes and steep outlet vanes,designed to handle higher percentages of entrained gas. In anotherembodiment the mixing pump (410) includes an inducer to aid in handlingthe gas rich mixture and reduce the likelihood of cavitation; while instill another embodiment these goals are addressed through the use of arecessed impeller; and in yet another embodiment a vortex typecentrifugal pump is used; while an even further embodiment utilizes aself-priming mixing pump.

The mixing system (400) is illustrated generically in FIGS. 2-4 as beingwithin the mixing tank (300), however this is not required. A smallscale test system and method are illustrated in FIGS. 6 and 16, in whichthe mixing system (400) is located within the mixing tank (300), howeverlarge scale implementation may require a portion of the mixing system(400) to be located external to the mixing tank (300), such asillustrated in the embodiments of FIGS. 7-9 and 17. The mixing system(400) may include a mixing pump (410) having an inlet and an outlet,wherein the inlet receives both unprocessed exhaust gas from the firstgas handling system (200) and system fluid (330) of the mixing tank(300). In such embodiments the mixing pump outlet, or discharge, is influid communication with the mixing tank (300).

The system and method of such embodiments includes the step of mixingunprocessed exhaust gas and system fluid (330) within the mixing pump(410) to create a mixed system fluid leaving the outlet and returningthe mixed system fluid to the system fluid within the mixing tank (300),either above the top surface elevation of the system fluid (330),including some embodiments returning the mixed system fluid via at leastone discharge nozzle (444) as seen in FIGS. 6-8, or below the topsurface elevation of the system fluid (330), such as that seen in theembodiment of FIG. 9. The mixing pump inlet may be in direct fluidcommunication with both unprocessed exhaust gas from the first gashandling system (200) and system fluid (330) of the mixing tank (300),as seen in the embodiments of FIGS. 6 and 7 which have a pump fluidinlet (420) and a pump gas inlet (430), or it may indirectly receive theunprocessed exhaust gas and system fluid, via an pump fluid inlet (420)that is open to the system fluid (330) within the mixing tank (300) andpositioned such that a portion of the unprocessed exhaust gas bubbleswithin the mixing tank (330) enter the pump fluid inlet (420) as seen inthe embodiments of FIGS. 8 and 9.

Some embodiments of the mixing system (400) include a bubble diffuser(460) within the mixing tank (300), with the bubble diffuser (460) isfluid communication with the first gas handling system (200), asillustrated in FIGS. 8 and 9. Thus, the unprocessed exhaust gas isdiffused into the system fluid (330) through the bubble diffuser (460)thereby creating unprocessed exhaust gas bubbles within the system fluid(330), and the mixing pump inlet draws system fluid (330) and a portionof the unprocessed exhaust gas bubbles into the mixing pump (410). Anadvantage of this embodiment is that some degree of treatment of theexhaust gas is performed before it enters the mixing pump (410).Further, the mixing pump (410) performs the violent shearing and mixingof the exhaust gas bubbles and may provide the previously discussed gasentrainment ranges and bubble sizes in the mixed discharge, therefore insome embodiments the bubble diffuser (460) is a coarse bubble diffuser(460) producing ¼ to ½ inch bubbles, which reduces the cleaning andmaintenance associated with the bubble diffuser (460). However, otherembodiments incorporate a fine bubble diffuser (460) producing bubblesof less than ¼ inch in diameter, further increasing the surface area andtreatment that occurs before entering the mixing pump (410). In fact,one embodiment incorporates a bubble diffuser (460) producing bubblediameters of less than 12 mm, while a further embodiment produces bubblediameters of less than 6 mm, and still another embodiment producesbubble diameters of less than 4 mm, and even less than 2 mm in a furtherembodiment. Placement of the bubble diffuser (460) within the mixingtank (300) with respect to the surface elevation of the system fluid(330) impacts the energy consumption of the system and method, andimpacts the type of equipment used in the first gas handling system(200), and specifically the first GHS fan (210). Thus, in one embodimentthe bubble diffuser (460) is no more than 36 inches below the surface ofthe mixing system fluid (330), while in another embodiment it is no morethan 24 inches below the surface of the mixing system fluid (330), andin yet a further embodiment it is no more than 12 inches below thesurface of the mixing system fluid (330). As illustrated in FIG. 9, inone embodiment the mixed system fluid leaving the mixing pump outlet isreturned to the system fluid within the mixing tank (300) at leastdistance below the surface of the mixing system fluid (330) that is atleast twice the distance that the bubble diffuser (460) is below thesurface of the mixing system fluid (330), while in another embodiment itis at least 3 times the distance that the bubble diffuser (460) is belowthe surface of the mixing system fluid (330), and at least 4 times inyet another embodiment. An advantage of such embodiments is thatmajority of the exhaust gas passes through the mixing pump (310) morethan once before reaching the surface of the system fluid (330) andleaving the mixing tank (300), further improving the efficiency andleaving more particulate and pollutants within the mixing tank (300).Further, at least one inlet guide plate (470) may be incorporated withinthe mixing tank (300) go gather upward rising bubbles and direct them tothe mixing pump (410), further making it more difficult for bubbles tomake it to the surface of the system fluid (330) and leave the mixingtank (300). The bubble diffuser (470) may consist of pipe or otheroutlet having a multitude of orifices located therein that allows theunprocessed exhaust gas to pass through, thereby forming small bubblesin the system fluid (330). As the unprocessed exhaust gas bubbles travelupwards through the system fluid (330) they are scrubbed of particulatematter. Furthermore, the small bubbles of exhaust gas providedsufficient surface area for various chemical reagents in the systemfluid (330) to react with the sulfur dioxide and other chemicals foundin the unprocessed exhaust gas. A further embodiment of the mixing tank(300) includes an impeller mixer, not shown, that further mixes andagitates the system fluid (330) in the mixing tank (300), and may forcesome of the bubbles towards the bottom of the tank, thereby increasingthe time that the exhaust gas bubbles spend in the system fluid (330).

In another series of embodiments the mixing pump outlet is in fluidcommunication with at least one discharge nozzle (444) located withinthe mixing tank (300) at an elevation above the system fluid (330), asseen in FIGS. 7 and 8. In such embodiments the highly gas entrainedmixed system fluid leaves the mixing pump (410) and is sprayed withinthe mixing tank (300) further scrubbing the exhaust gas before it exitsthe mixing tank (300), also improving the efficiency and leaving moreparticulate and pollutants within the mixing tank (300). In still afurther embodiment, not illustrated but easily understood as acombination of the previously discussed embodiments, the mixing pumpoutlet is in fluid communication with both (a) at least one dischargenozzle (444) located within the mixing tank (300) at an elevation abovethe surface system fluid (330), and (b) a mixed system fluid dischargethat is below the surface of the system fluid (330). In such anembodiment the mixing tank control system may control the percentage ofthe flow leaving the mixing pump (410) that returns to the mixing tank(300) via either system based upon input from the sensors.

As illustrated in FIGS. 7-9, the pump fluid inlet (420) may include afluid inlet control valve (422), the pump gas inlet (430) may include agas inlet control damper (432), and the pump discharge (440) may includea discharge control valve (442), all of which may be manually orautomatically controlled, via the mixing tank control system, to achievethe desire exhaust gas entrainment. The system and method may furtherinclude an entrained gas sensor (450), as seen in FIG. 7, to monitor theamount of entrained gas in the mixed system fluid discharged from themixing pump (410), and automatically adjust, via an entrainment controlsystem or module of the mixing tank control system, the fluid inletcontrol valve (422) and/or the gas inlet control damper (432) to achievethe desire exhaust gas entrainment.

Referring back to the embodiment illustrated in FIG. 6, here the mixingpump inlet is direct fluid communication with both unprocessed exhaustgas from the first gas handling system (200) and system fluid (330) ofthe mixing tank (300). In this embodiment the first gas handling system(200) has at least one first GHS outlet (204), which is directlyconnected to the inlet of the mixing pump (410). In the illustratedembodiment at least one orifice (480) is incorporated in the first gashandling system (200) near the GHS outlet (204). The entry of the firstgas handling system (200) into the mixing tank (300) above the elevationof the system fluid (330), and the location of the at least one orifice(480), are such that system fluid (330) cannot flood the first gashandling system (200), and operation of the mixing pump (410) drawssystem fluid (330) from the mixing tank (300) through the at least oneorifice (480), while also drawing unprocessed exhaust gas into themixing pump (410). One skilled in the art will appreciate that this mayalso be accomplished via a control valve, also referred to as abalancing valve or throttling valve, with the valve opening constitutingthe at least one orifice (480). The U-shaped configuration of the firstgas handling system (200) within the mixing tank (300) prevents systemfluid (330) from filling the first gas handling system (200) when themixing pump (410) is not operating, and a portion of which is quicklyevacuated by the mixing pump (410) upon start up. In this embodiment thedischarge from the mixing pump (410) is in fluid communication with atleast one discharge nozzle (444) that sprays the gas entrained mixedsystem fluid back into the mixing tank (300). Although illustrated as asubmersible pump within the mixing tank (300), all, or portions of, themixing system (400) may be located outside of the mixing tank (300).

In one embodiment the entry of the first gas handling system (200) intothe mixing tank (300) is above the elevation of the system fluid (330),as seen in FIGS. 16-17, and includes a submerged GHS section (220)within the system fluid (330). This is beneficial for many reasonsincluding providing a unique method of combining the unprocessed exhaustgas and the system fluid (330) prior to entry into the mixing pump(410). The submerged GHS section (220) may include a submerged GHSdirectional change (230), which in one embodiment changes the directionof flow by at least 45 degrees, at least 90 degrees in a furtherembodiment, at least 135 degrees in still another embodiment, and atleast 180 degrees in yet a further embodiment. The submerged GHS section(220) may further include at least one auxiliary flow channel (240)having an auxiliary flow channel inlet (242), an auxiliary flow channeloutlet (244), and in some embodiments an auxiliary flow channeldirectional change (246), which in one embodiment changes the directionof flow by at least 45 degrees, at least 90 degrees in a furtherembodiment, at least 135 degrees in still another embodiment, and atleast 180 degrees in yet a further embodiment. The at least oneauxiliary flow channel (240) extends within the first gas handlingsystem (200) from the auxiliary flow channel inlet (242) at a pointabove the elevation of the system fluid (330) within the mixing tank(300), downward below the elevation of the system fluid (330) within themixing tank (300), to the auxiliary flow channel outlet (244), which ispositioned such that the unprocessed exhaust gas may rise and mix withsystem fluid (330) to either the entry to the mixing pump (410) or thetransition to the pump fluid inlet (420), as seen in FIG. 17. In oneembodiment the auxiliary flow channel outlet (244) is preferably locatedat a submerged GHS directional change (230), while in a furtherembodiment the auxiliary flow channel outlet (244) is preferably locatedadjacent to the at least one mixing system orifice (480). In a furtherembodiment the auxiliary flow channel outlet (244) is preferably locatedat an auxiliary flow channel directional change (246) of at least 30degrees and allows the unprocessed exhaust gas to rise substantiallyvertically to the entry to the mixing pump (410) or the transition tothe pump fluid inlet (420).

In one embodiment the at least one auxiliary flow channel (240) has across-sectional flow area, perpendicular to the direction of flow, thatis at least 5% of a submerged GHS section (220) cross-sectional flowarea, also perpendicular to the direction of flow, while in a furtherembodiment it is at least 10%, and at least 15% in still anotherembodiment. In another series of embodiments the auxiliary flow channelcross-sectional flow area is no more than 70% of the submerged GHSsection cross-sectional flow area, and no more than 60% in anotherembodiment, and no more than 50% in still a further embodiment. The atleast one orifice (480) is an opening in the submerged GHS section (220)that allows system fluid (330) to enter the submerged GHS section (220),wherein in one embodiment the at least one orifice (480) is located onthe lower 180 degrees of the circumference of the submerged GHS section(220) and no orifices (480) are located on the upper 180 degrees of thecircumference, thereby promoting flow within the submerged GHS section(220) that facilitates flow of the exhaust gas. Each orifice (480) hasan orifice open area, or flow area, and in one embodiment that totalorifice open area of all of the orifices is at least equal to theauxiliary flow channel cross-sectional flow area, while in a furtherembodiment the total orifice open area of all of the orifices is no morethan six times the auxiliary flow channel cross-sectional flow area,while in yet a further embodiment the total orifice open area of all ofthe orifices is 2-4 times the auxiliary flow channel cross-sectionalflow area. Even further, in another embodiment the total orifice openarea of all of the orifices, in square inches, is at least 0.025 timesthe flowrate, in gpm, of the mixing pump (410), while in anotherembodiment it is 0.025-0.09, and is at least 0.040 in still a furtherembodiment, and 0.040-0.065 in yet another embodiment. These uniquerelationships and changes in flow direction ensure that upon start-upthe mixing pump (410) can evacuate system fluid (330) from the auxiliaryflow channel (240) and create a passageway for the unprocessed exhaustgas, and during normal operation they facilitate the creating ofpreferred fluid paths, reduce the risk of air locks, ensure largepockets of unprocessed exhaust gas don't damage the mixing pump, andprovide appropriate proportioning to achieve the desired entrainmentwithin the mixed discharge exiting the mixing pump (410).

As previously noted, FIG. 6 illustrates the configuration of a smallscale test configuration of the system and method. In the test setup themixing tank (300) is approximately 300 gallons, containing approximately225 gallons of system fluid (330). The test setup included variationswith a mixing pump (410) that a 30 gpm submersible pump, and a variationwith a 157 gpm external pump. The unprocessed exhaust gas were generatedin a source (100) consisting of a fire box burning approximately 30pounds of bituminous coal mined in the state of Ohio. With reference nowto FIG. 4, Tables 1 and 2 represent the contents of unprocessed exhaustgas in the test setup sampled at the exit of the source (100). Testingof the system fluid (330) was performed after operation of the systemfor several hours and revealed a sulfate concentration in the systemfluid (330) of 156.7 mg/L.

TABLE 1 Result MRL Compound %, v/v %, v/v 7727-37-9 Nitrogen 78.8 0.14630-08-0 Carbon Monoxide 0.205 0.14 124-38-9 Carbon Dioxide 3.45 0.14 ND= Compound was analyzed for, but not detected above the laboratoryreporting limit. MRL = Method Reporting Limit - The minimum quantity ofa target analyte that can be confidently determined by the referencedmethod.

TABLE 2 Result MRL Result MRL Compound μg/m³ μg/m³ ppbV ppbV 115-07-1Propene 43,000 690 25,000 400 75-71-8 Dichlorodifluoromethane (CFC 12)ND 69 ND 14 74-87-3 Chloromethane 160 69 79 33 76-14-21,2-Dichloro-1,1,2,2- ND 69 ND 9.8 tetrafluoroethane (CFC 114) 75-01-4Vinyl Chloride 74 69 29 27 106-99-0 1,3-Butadiene 4,300 69 2,000 3174-83-9 Bromomethane ND 69 ND 18 75-00-3 Chloroethane ND 69 ND 2664-17-5 Ethanol ND 690 ND 360 75-05-8 Acetonitrile 780 69 470 41107-02-8 Acrolein 900 270 390 120 67-64-1 Acetone 2,900 690 1,200 29075-69-4 Trichlorofluoromethane (CFC ND 69 ND 12 11) 67-63-0 2-Propanol(Isopropyl Alcohol) ND 690 ND 280 107-13-1 Acrylonitrile 580 69 270 3275-35-4 1,1-Dichloroethene ND 69 ND 17 75-09-2 Methylene Chloride ND 69ND 20 107-05-1 3-Chloro-1-propene (Allyl ND 69 ND 22 Chloride) 76-13-1Trichlorotrifluoroethane (CFC ND 69 ND 8.9 113) 75-15-0 Carbon Disulfide3,800 690 1,200 220 156-60-5 trans-1,2-Dichloroethene ND 69 ND 1775-34-3 1,1-Dichloroethane ND 69 ND 17 1634-04-4 Methyl tert-Butyl EtherND 69 ND 19 108-05-4 Vinyl Acetate ND 690 ND 190 78-93-3 2-Butanone(MEK) 790 690 270 230Tables 3 and 4 represent the contents of diffused processed exhaust gasin the test setup sampled at the exit of the diffusion chamber (700).

TABLE 3 Result MRL Compound %, v/v %, v/v 7727-37-9 Nitrogen 77.7 0.14630-08-0 Carbon Monoxide ND 0.14 124-38-9 Carbon Dioxide ND 0.14 ND =Compound was analyzed for, but not detected above the laboratoryreporting limit. MRL = Method Reporting Limit - The minimum quantity ofa target analyte that can be confidently determined by the referencedmethod.

TABLE 4 Result MRL Result MRL Compound μg/m³ μg/m³ ppbV ppbV 115-07-1Propene 33 1.9 19 1.1 75-71-8 Dichlorodifluoromethane (CFC 12) 2.6 1.90.52 0.39 74-87-3 Chloromethane ND 1.9 ND 0.93 76-14-21,2-Dichloro-1,1,2,2- ND 1.9 ND 0.28 tetrafluoroethane (CFC 114) 75-01-4Vinyl Chloride ND 1.9 ND 0.75 106-99-0 1,3-Butadiene 3.9 1.9 1.8 0.8774-83-9 Bromomethane ND 1.9 ND 0.50 75-00-3 Chloroethane ND 1.9 ND 0.7364-17-5 Ethanol ND 19 ND 10 75-05-8 Acetonitrile 3.2 1.9 1.9 1.1107-02-8 Acrolein ND 7.7 ND 3.4 67-64-1 Acetone 37 19 16 8.1 75-69-4Trichlorofluoromethane (CFC ND 1.9 ND 0.34 11) 67-63-0 2-Propanol(Isopropyl Alcohol) ND 19 ND 7.8 107-13-1 Acrylonitrile ND 1.9 ND 0.8975-35-4 1,1-Dichloroethene ND 1.9 ND 0.49 75-09-2 Methylene Chloride ND1.9 ND 0.55 107-05-1 3-Chloro-1-propene (Allyl ND 1.9 ND 0.62 Chloride)76-13-1 Trichlorotrifluoroethane (CFC ND 1.9 ND 0.25 113) 75-15-0 CarbonDisulfide ND 19 ND 6.2 156-60-5 trans-1,2-Dichloroethene ND 1.9 ND 0.4975-34-3 1,1-Dichloroethane ND 1.9 ND 0.48 1634-04-4 Methyl tert-ButylEther ND 1.9 ND 0.53 108-05-4 Vinyl Acetate ND 19 ND 5.5 78-93-32-Butanone (MEK) ND 19 ND 6.5

While the operation of the mixing system (400) significantly cools theexhaust gas, any of the embodiments disclosed may also incorporate anexhaust gas cooling system in the first gas handling system (200) toreduce the temperature of the unprocessed exhaust gas before it reachesthe mixing system (400). The exhaust gas cooling system may utilize thesystem fluid (330) as a cooling medium, or may utilize an externalcooling medium, which may be air or liquid.

During the mixing process, particulate matter and pollutants in theunprocessed exhaust gas are separated out and remain in the system fluid(330). Furthermore, various chemicals in the unprocessed exhaust gas andany system fluid additives, or chemical reagents, such as, but notlimited to, hydrated lime (Ca(OH)₂) are violently mixed in the mixingpump (410), resulting in efficient sulfur dioxide scrubbing of theunprocessed exhaust gas. After the combination of system fluid (330) andexhaust gas passes through the mixing pump (410) the mixed system fluidexits the pump and returns to the mixing tank (300). The particulatesolids and chemical precipitates stay in the system fluid (330) andsettle to the bottle of the mixing tank (300) and the processed exhaustgas eventually makes its way to the upper section of the mixing tank(300). The tank settlement may then be drained and captured on acollection system (1000), such as the conveyor system (1000) illustratedin FIG. 7, which may transport the particulate to a drying bed, whichmay be heated, to dry and separate the materials so that they may besold or properly disposed of.

In another embodiment of the mixing system (400), not illustrated, themixing system (400) uses the venturi effect wherein system fluid (330)is pumped through one or more venturies creating a vacuum which drawsthe unprocessed exhaust gas through the one or more venturies to mixwith the system fluid (300). As a result the unprocessed exhaust gas andsystem fluid (330) become thoroughly mixed, and may obtain thepreviously disclosed entrained gas and bubble properties.

In another embodiment, after the unprocessed exhaust gas passes throughthe mixing system (400), the now scrubbed and processed gas is conveyedto a diffusion chamber (700) by a second gas handling system (600), asseen in FIG. 4. The second gas handling system (600) includes a secondgas handling system inlet (602) which is in communication with themixing tank (300), and a second gas handling system outlet (604) incommunication with the diffusion chamber (700), or a cooling tower, asseen in FIG. 3. Furthermore, the second gas handling system (600) mayinclude a second gas handling system fan (610) having a second gashandling system flowrate, seen in FIGS. 4 and 5, which in someembodiments creates a negative pressure in portion of the mixing tank(300) above the surface of the system fluid (330), and moves theprocessed exhaust gas from the mixing tank (300) to the diffusionchamber (700), which in some embodiments is a cooling tower.

The diffusion chamber (700) replaces the function of an exhaust stackcommonly found in power plants. Traditionally, exhaust stacks deliverthe exhaust gas into a high elevation in relation to the ground level.This allows the exhaust gases to mix with air in the atmosphere anddisperse. The diffusion chamber (700) replaces the exhaust gas stackwith a large enclosed space that may include a baffling system and fansto introduce fresh atmospheric air into the diffusion chamber (700). Asthe processed exhaust gas enters the diffusion chamber (700) from thesecond gas handling system (600), the exhaust gas is diluted and cooled.In some embodiment the diffusion chamber (700) includes at least onediffusion chamber fan (710), seen in FIG. 10, introducing freshatmospheric air, at a fresh air flowrate, into the diffusion chamber(700) to mix with the processed exhaust gas. In one particularembodiment the fresh air flowrate is at least 5 times the second gashandling system flowrate, while in another embodiment the fresh airflowrate is at least 10 times the second gas handling system flowrate,while in still another embodiment the fresh air flowrate is at least 20times the second gas handling system flowrate. In another embodiment thefresh air flowrate is at least 5 times the first gas handling systemflowrate, while in another embodiment the fresh air flowrate is at least10 times the first gas handling system flowrate, while in still anotherembodiment the fresh air flowrate is at least 20 times the first gashandling system flowrate. The diffusion chamber (700) also has adiffusion chamber volume, which is the internal volume of the flow pathfrom the entrance to the exit measured in cubic feet. In one embodimentthe diffusion chamber volume is at least 1 cubic foot for every cubicfeet per minute (CFM) of the second gas handling system flowrate, whilein another embodiment the diffusion chamber volume is at least 2 cubicfeet for every CFM of the second gas handling system flowrate, and inyet a further embodiment the diffusion chamber volume is at least 5cubic feet for every CFM of the second gas handling system flowrate. Inone embodiment the diffusion chamber volume is at least 1 cubic foot forevery cubic feet per minute (CFM) of the first gas handling systemflowrate, while in another embodiment the diffusion chamber volume is atleast 2 cubic feet for every CFM of the first gas handling systemflowrate, and in yet a further embodiment the diffusion chamber volumeis at least 5 cubic feet for every CFM of the first gas handling systemflowrate. In still another series of embodiments the diffusion chambervolume is at least 1 cubic foot for every cubic feet per minute (CFM) ofthe fresh air flowrate, while in another embodiment the diffusionchamber volume is at least 2 cubic feet for every CFM of the fresh airflowrate, and in yet a further embodiment the diffusion chamber volumeis at least 5 cubic feet for every CFM of the fresh air flowrate.

The diffusion chamber (700) may incorporate a flow path that requiresnumerous changes in direction. In fact, in one embodiment the diffusionchamber (700) requires at least two ninety degree changes in direction,while in a further embodiment requires at least two 180 degree changesin direction, while an even further embodiment incorporates amulti-level routing so that the exhaust gas must pass through a firstlevel to exit and exhaust gas outlet aperture (720) leading to at leaston additional level requiring a similar air path, as seen in FIGS. 12and 13. In some embodiments each level is capable of being isolated soall levels are not utilized during periods of low load, which may becontrolled manually or automatically by a diffusion chamber controlsystem. In still a further embodiment a one diffusion chamber fan (710)introduces fresh air at one or more of the changes in direction toassist in diffusing the exhaust gas and moving the exhaust gas throughthe diffusion chamber (700), while in a further embodiment a diffusionchamber fan (710) introduces fresh air at each of the changes indirection. The diffusion chamber (700) may further include at least onestatic mixing device in the flow path to further mix the exhaust gas andfresh air, and reduce stratification within the diffusion chamber (700),which in some further embodiments is accomplished via in-line fanslocated within the flow path. A benefit of the diffusion chamber (700)is that it permits the discharge of the exhaust gas at significantlylower elevations than traditional exhaust stacks. In fact, in oneembodiment the discharge from the diffusion chamber (700) is at anelevation of less than 100 feet above the adjacent ground level, whilein a further embodiment the discharge elevation is less than 75 feet,and less than 50 feet in still a further embodiment, and less than 25feet in a final embodiment.

The unprocessed exhaust gas enters the mixing system (400) at anunprocessed exhaust gas temperature, and the processed exhaust gasleaves the mixing tank (300) at a processed exhaust gas temperature. Inone embodiment the processed exhaust gas temperature is less than 75% ofthe unprocessed exhaust gas temperature, while in a further embodimentthe processed exhaust gas temperature is less than 50% of theunprocessed exhaust gas temperature. Additionally, in another embodimentthe discharge from the diffusion chamber (700) is cooled to a dischargegas temperature of no more than 300 degrees Fahrenheit, and no more than200 degrees Fahrenheit in another embodiment, and no more than 150degrees Fahrenheit in still a further embodiment. In some embodimentsthe discharge gas temperature is no more than 40% of the unprocessed gastemperature, and not more than 30% of the unprocessed gas temperature inanother embodiment, and not more than 20% of the unprocessed gastemperature in still a further embodiment. The diffusion chamber (700),and any of the gas handling systems, may include sensors to monitor any,or all, of the following: carbon monoxide, lead, ground-level ozone,nitrogen dioxide, particulate matter, sulfur dioxide, and temperature.If the pollutants exceed acceptable levels the fresh air flow maybeincreased to further dilute the exhaust gas, and/or part of the exhaustgas may be recirculated back to a secondary mixing system (400 b) forfurther scrubbing, as illustrated in FIG. 14 which incorporates a thirdgas handling system (800) having a third GHS inlet (802) incommunication with the diffusion chamber (700), a third GHS outlet (804)in communication with second mixing tank (300 b), and a third GHS fan(810) to transfer exhaust gas from the diffusion chamber (700) to thesecond mixing tank (300 b), as well as a fourth gas handling system(900) having a fourth GHS inlet (902) in communication with the secondmixing tank (300 b), and a fourth GHS outlet (904) in communication withthe second gas handling system (600). In some embodiments the fourth gashandling system (900) may incorporate a fourth gas handling system fan,not shown, to aid in returning exhaust gas from the second mixing tank(300 b) to the second gas handling system (600). Alternatively, inseries mixing tank embodiments, the second gas handling system (600) maytransfer exhaust gas from one mixing tank (300 a) to another mixing tank(300 b), while in a further embodiment the third gas handling system(800) may transfer exhaust gas from the second mixing tank (300 b) to athird mixing tank (300 c), and so forth; with the embodiment of FIG. 15then having the fourth gas handling system (900), analogous to thesecond gas handling system (600) in FIG. 4, then transferring exhaustgas to the diffusion chamber (700) or cooling tower.

The system and method may include a diffusion chamber control systemthat modulates the fresh air flowrate, either by turning on and off, ormodulating, the at least one diffusion chamber fan (710) in response toany of the disclosed sensors to achieve the desired dischargeconditions, as well as the dampers and fans of the third gas handlingsystem (800) and fourth gas handling system (900) in recirculatingembodiments, such as that of FIG. 14, or series mixing tank embodiments,such as that of FIG. 15. The diffusion chamber control system may beprogrammed to record and adjust operating parameters of the system andmethod to meet the limits defined in the National Ambient Air QualityStandards (NAAQS) for six principal pollutants.

In another embodiment, the diffusion chamber (700) utilizes a heatexchanger (730) to further cool the exhaust gases, seen in FIG. 11;further, a heat exchanger may also be incorporated in any of the gashandling systems. Economic efficiency of a power plant can be increasedby capturing waste heat and using it to preheat the boiler water that isturned into steam. As a result, the exhaust gases are further cooled andhave lower local environmental heating which may adversely impact theenvironment. In one particular embodiment at least a portion of thediffusion chamber (700) is below ground to aid in cooling the exhaustgas, while in a further embodiment majority of the diffusion chamber(700) is below ground.

After the exhaust gas has been sufficiently clean, diluted and cooled tomeet NAAQS standards, the gas is released into the atmosphere. In orderto sequester carbon dioxide being released from the diffusion chamber(700), vegetation that has high carbon dioxide absorption capabilitiesmay be planted around, or within, the diffusion chamber (700). Forexample, common horse-chestnut, black walnut, American sweetgum,ponderosa pine, red pine, white pine, London plane, Hispaniola pine,Douglas fir, scarlet oak, red oak, Virginia live oak, bald cypress,bamboo and hemp readily absorb and store carbon dioxide. The vegetationalso provides an added benefit of noise attenuation. Carbonsequestration can be enhanced by using a diffusion chamber (700) insteadof an exhaust stack because it releases carbon dioxide (CO₂) at groundlevel near the carbon dioxide (CO₂) absorbing vegetation, unlike anexhaust stack which releases it high in the atmosphere. Alternatively,the processed exhaust gas leaving the mixing tank (300) may be routedvia the second gas handling system (600) to an onsite cooling tower, asseen in FIG. 3. The present system and method achieves the stated goalwithout the use of filters or collection plates, both of which requirecontinuous maintenance.

Numerous alterations, modifications, and variations of the preferredembodiments disclosed herein will be apparent to those skilled in theart and they are all anticipated and contemplated to be within thespirit and scope of the disclosed specification. For example, althoughspecific embodiments have been described in detail, those with skill inthe art will understand that the preceding embodiments and variationscan be modified to incorporate various types of substitute and oradditional or alternative materials, relative arrangement of elements,order of steps and additional steps, and dimensional configurations.Accordingly, even though only few variations of the method and productsare described herein, it is to be understood that the practice of suchadditional modifications and variations and the equivalents thereof, arewithin the spirit and scope of the method and products as defined in thefollowing claims. Further, steps within a method using the language “thestep of maintaining” or “monitoring” are not to be construed asautomatically adjusting to achieve a specified value, range, orrelationship, but rather may be achieved, and within the scope of theclaims, solely due to the design of the structure, components, orattributes thereof. The corresponding structures, materials, acts, andequivalents of all means or step plus function elements in the claimsbelow are intended to include any structure, material, or acts forperforming the functions in combination with other claimed elements asspecifically claimed.

We claim:
 1. A method for reduction of particulate and contaminants from exhaust gas comprising: a) conveying unprocessed exhaust gas, at an unprocessed exhaust gas temperature, from a source (100) to a mixing tank (300), containing a system fluid, via a first gas handling system (200) having a first gas handling system flowrate, a first GHS inlet (202) in communication with the source (100), and a first GHS outlet (204) in communication with a mixing system (400), wherein the mixing system (400) mixes the unprocessed exhaust gas and the system fluid, while agitating the system fluid, wherein: i) the mixing tank (300) has a mixing tank liquid volume of at least 0.1 gallon per CFM of the first gas handling system flowrate, and a mixing tank gas volume of at least 0.013 cubic feet per CFM of the first gas handling system flowrate and at least 50% of the mixing tank liquid volume; ii) the mixing system (400) includes a mixing pump (410) having a mixing pump flowrate, an inlet, and an outlet, wherein the inlet receives a mixture of both unprocessed exhaust gas from the first gas handling system (200) and system fluid of the mixing tank (300), and the outlet is in fluid communication with the mixing tank (300); iii) the first gas handling system (200) includes a submerged GHS section (220) below the elevation of the system fluid, the submerged GHS section (220) includes a submerged GHS directional change of at least 45 degrees and contains an auxiliary flow channel (240) having (a) an auxiliary flow channel inlet (242) above the elevation of the system fluid, and (b) an auxiliary flow channel outlet (244) below the elevation of the system fluid, the submerged GHS section (220) having at least one orifice (480) allowing flow of system fluid from the mixing tank (300) into the submerged GHS section (220); iv) further including the steps of drawing unprocessed exhaust gas through at least the auxiliary flow channel (240) and drawing system fluid through the at least one orifice (480), and mixing unprocessed exhaust gas and system fluid within the mixing pump (410) via a rotating pump impeller to create a mixed system fluid leaving the outlet with entrained gas and returning the mixed system fluid to the system fluid within the mixing tank (300); b) conveying processed exhaust gas at a processed exhaust gas temperature that is less than 75% of the unprocessed exhaust gas temperature, from the mixing tank (300) to a diffusion chamber (700) via a second gas handling system (600) having a second GHS inlet (602) in communication with the mixing tank (300), and a second GHS outlet (604) in communication with the diffusion chamber (700); c) mixing the processed exhaust gas with fresh atmospheric air, having a fresh air flowrate, in the diffusion chamber (700) to create a discharge gas having a discharge gas temperature below 300 degrees Fahrenheit and less than 40% of the unprocessed exhaust gas temperature; and d) releasing the discharge gas from the diffusion chamber (700).
 2. The method of claim 1, wherein the auxiliary flow channel (240) includes an auxiliary flow channel directional change (246) of at least 30 degrees.
 3. The method of claim 2, wherein the step of drawing unprocessed exhaust gas through the auxiliary flow channel (240) further includes changing the direction of flow at least 90 degrees before exiting the auxiliary flow channel outlet (244).
 4. The method of claim 1, wherein the mixing tank liquid volume is circulated at least once every hour.
 5. The method of claim 4, further including the step of maintaining the mixing tank liquid volume to no more than 5.0 gallons per CFM of the maximum first gas handling system flowrate.
 6. The method of claim 1, further including the step of maintaining the mixing tank gas volume to be greater than the mixing tank liquid volume.
 7. The method of claim 6, further including the step of maintaining the mixing tank gas volume to no more than twice the mixing tank liquid volume.
 8. The method of claim 1, further including the step of maintaining the maximum mixing pump flowrate at 0.5-50 GPM per CFM of the maximum first gas handling system flowrate.
 9. The method of claim 1, further including the step of maintaining the mixed system fluid to contain 6-30% exhaust gas entrained in the mixed system fluid.
 10. The method of claim 1, wherein the diffusion chamber volume is at least 1 cubic foot per CFM of the fresh air flowrate and at least 1 cubic foot per CFM of the first gas handling system flowrate.
 11. The method of claim 1, further including the step of automatically adjusting the amount of unprocessed exhaust gas drawn through at least the auxiliary flow channel (240) to achieve a target percentage of entrained gas within the mixed system fluid.
 12. The method of claim 1, further including the step of automatically adjusting the amount of system fluid drawn through the at least one orifice (480) to achieve a target percentage of entrained gas within the mixed system fluid.
 13. The method of claim 1, wherein the first gas handling system (200) enters the mixing tank (300) above an elevation of the system fluid.
 14. The method of claim 1, wherein the at least one orifice (480) has an orifice open area of 0.025-0.09 square inches per GPM of the mixing pump flowrate.
 15. The method of claim 1, wherein the step of mixing unprocessed exhaust gas and system fluid within the mixing pump (410) produces an average bubble size of the entrained exhaust gas of less than 100 μm.
 16. A method for reduction of particulate and contaminants from exhaust gas comprising: a) conveying unprocessed exhaust gas, at an unprocessed exhaust gas temperature, from a source (100) to a mixing tank (300), containing a system fluid, via a first gas handling system (200) having a first gas handling system flowrate, a first GHS inlet (202) in communication with the source (100), and a first GHS outlet (204) in communication with a mixing system (400), wherein the mixing system (400) mixes the unprocessed exhaust gas and the system fluid, while agitating the system fluid, wherein: i) the mixing tank (300) has a mixing tank liquid volume of at least 0.1 gallon per CFM of the first gas handling system flowrate, and a mixing tank gas volume of at least 0.013 cubic feet per CFM of the first gas handling system flowrate and at least 50% of the mixing tank liquid volume, and further including the step of maintaining the mixing tank gas volume to be greater than the mixing tank liquid volume; ii) the mixing system (400) includes a mixing pump (410) having a mixing pump flowrate of at least 0.5 GPM per CFM of the maximum first gas handling system flowrate, an inlet, and an outlet, wherein the inlet receives a mixture of both unprocessed exhaust gas from the first gas handling system (200) and system fluid of the mixing tank (300), the outlet is in fluid communication with the mixing tank (300), and the mixing pump (410) circulates the mixing tank liquid volume at least once every hour; iii) the first gas handling system (200) includes a submerged GHS section (220) below the elevation of the system fluid, the submerged GHS section (220) includes a submerged GHS directional change of at least 45 degrees and has at least one orifice (480) allowing flow of system fluid from the mixing tank (300) into the submerged GHS section (220); iv) further including the steps of drawing unprocessed exhaust gas through at least the submerged GHS section (220) and drawing system fluid through the at least one orifice (480), and mixing unprocessed exhaust gas and system fluid within the mixing pump (410) via a rotating pump impeller to create a mixed system fluid leaving the outlet with entrained gas and returning the mixed system fluid to the system fluid within the mixing tank (300); b) conveying processed exhaust gas at a processed exhaust gas temperature that is less than 75% of the unprocessed exhaust gas temperature, from the mixing tank (300) to a diffusion chamber (700) via a second gas handling system (600) having a second GHS inlet (602) in communication with the mixing tank (300), and a second GHS outlet (604) in communication with the diffusion chamber (700); and c) mixing the processed exhaust gas with fresh atmospheric air, having a fresh air flowrate, in the diffusion chamber (700) to create a discharge gas having a discharge gas temperature less than 40% of the unprocessed exhaust gas temperature.
 17. The method of claim 16, wherein the submerged GHS section (220) includes a submerged GHS directional change of at least 90 degrees.
 18. The method of claim 16, further including the step of maintaining the mixing tank liquid volume to no more than 5.0 gallons per CFM of the maximum first gas handling system flowrate.
 19. The method of claim 16, further including the step of maintaining the mixing tank gas volume to no more than twice the mixing tank liquid volume.
 20. The method of claim 16, further including the step of maintaining the mixed system fluid to contain 6-30% exhaust gas entrained in the mixed system fluid, and wherein the step of mixing unprocessed exhaust gas and system fluid within the mixing pump (410) produces an average bubble size of the entrained exhaust gas of less than 100 μm. 